The present invention relates to a slip-controlled brake system for automotive vehicles with at least one static brake circuit into which pressure fluid out of a dynamic pressure fluid circuit can be introduced during slip control. The system includes a brake pressure generator comprising a master cylinder assembly and a hydraulic brake power booster with a control valve and with a booster piston which is adapted to be coupled with the brake pedal. At least one dynamic brake circuit is connected to the booster chamber.
Known multi-circuit brake systems operating according to the principle of dynamic flow-in into a brake circuit, and wherein the dynamic pressure corresponds to the pressure acting as well on the hydraulic booster piston, are disadvantageous in that in the event of a failure of this specific circuit, both the boosting effect and the braking effect of this circuit are lost.
In addition, brake systems have been proposed German printed and published patent application No. 3507484 which comprise a pedal-actuated brake power booster connected to the master cylinder. The booster being provided with a booster piston and a booster chamber, wherein an auxiliary pressure which is proportional to the pedal effort is generated by way of a brake valve. These systems are equipped with a fast-fill cylinder provided with a stepped bore, wherein a two-step piston is displaceably arranged, a pressure chamber is provided in front of the large step of the two-step piston and a filling chamber is provided in front of the small step. In this case, the pressure chamber is connected to the booster chamber and the filling chamber to a working chamber of the master cylinder, a non-return valve is inserted into the communicating conduit connecting the booster chamber with the pressure chamber of the fast-fill cylinder, and the control slide of the brake valve cooperates with a valve body through the intermediary of which the brake valve is connected to the pressure chamber. This known brake system is disadvantageous in that it requires a relatively large installation space since the fast-fill cylinder is designed as an additional separate unit.
The present invention has as an object to create a brake system of the type described, wherein in the event of a failure of the auxiliary pressure source a brake pressure can still be built up in the dynamic brake circuit connected to the hydraulic booster by means of the pedal effort so that the brakability of all wheel brakes will be maintained. The brake system should have a particularly simple design, should operate without complicated additional parts, and should be designed such that existing brake systems can be retrofitted with a hydraulic booster.